1. Field
This disclosure relates generally to non-volatile memory devices, and more specifically, to dynamic programming for flash memory.
2. Related Art
Semiconductor memory devices are used in a wide variety of electronic devices such as portable telephones, digital cameras, mobile and stationary computing devices, automobiles, appliances, and other devices. Non-volatile memory is a type of electronic memory that can be rewritten and hold data without power. One kind of non-volatile memory cell is consist of floating gate structure that is configured adjacent an insulated channel region in a semiconductor substrate. The channel region is positioned between source and drain regions. A control gate is provided over an insulated region above the floating gate. The threshold voltage of the memory is controlled by the amount of charges that retained on the floating gate. That is, the amount of charges in the floating gate determines the minimum voltage that must be applied on the control gate before the memory cell channel conducts between the source and drain regions. The memory cells can be programmed and erased between two states. Although the threshold voltage of each state is in theory the same for all memory cells, the reality is that some memory cells are programmed or erased faster than others, resulting in a distribution of threshold voltage for each state. Because of this, it is desired to adjust the width of the threshold voltage distribution as tight as possible to allow more read margin and less leakage current, which unfortunately, is a time consuming process. Additionally, it is quite common that the time spent adjusting the distribution width depends on the number of refresh cycles the memory cells have been experienced, the operating temperature of the memory device, and the process used to manufacture the memory cells.